DNA Replicatio1 - These different sources of damage lead to...

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DNA Replication Types of DNA Damage After DNA has been completely replicated, the daughter strand is often not a perfect copy of the parent strand it came from. Mutations during replication and damage after replication make it necessary for there to be a repair system to fix any errors in newly synthesized DNA. There are three main sources of damage to DNA. 1. Attack by water which can lead to the removal of an amine group from the base group of a nucleotide or the loss of the entire base group. 2. Chemical damage that permanently alters the structure of the DNA. 3. Radiation damage which can lead to nicks in the backbone of DNA or the formation of thymine dimers, which will be discussed later.
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Unformatted text preview: These different sources of damage lead to different categories of DNA damage. The damage that is caused by water attack can lead to unnatural bases. Chemical and radiation damage leads to the formation of bulky adducts to, or breaks in, the growing DNA strand. In the previous section we discussed the 3' to 5' proof-reading exonuclease that is responsible for fixing mismatches. Because it is not a perfect system, it can miss mismatched bases. As a result, a third category of DNA damage is mismatched bases. Repair Systems Because these categories of DNA damage are different, there is a need for multiple repair systems....
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